Wondered if anyone with bathroom remodel experience could guide me a bit on this one!

We have several time-sensitive issues in our bathroom that need to be addressed: there's mildew forming on the walls above the tub/shower because the paint is not designed to take the moisture (and possibly because we chose poorly in placing our new fan in the center of the small room rather than right over the shower, but that's another story!), our faucet valve is incorrectly installed (also another long story) such that we have a 1/2" gap between the faucet trim and the tile, and our tile grout is in not-so-hot shape and needs to be replaced in some spots (and maybe throughout).

It seems like a logical plan might be to retile the whole tub enclosure, run the tile up to the ceiling on the two walls where we have mildew/moisture issues, and add a little extra backer board on the wall with the faucet to pick up the extra half inch so everything sits flush there. (We could also take out and reinstall the valve, but not sure that it's necessary.)

The problem? My other half would like to gut the entire bathroom in five years or so and replace the standard tub with a freestanding clawfoot tub, so he thinks investing anything in it now is a waste of money. My concerns are that we may be causing some long-term damage by not adequately addressing the mildew and moisture issues now....and, given that the remodel would purely be cosmetic since everything was redone in a basic Home Depot style in the mid-1990s and works fine except for these issues, it may be so low on the to-do list that it never actually happens. (It's also our only bathroom.)

So this is the question--if we go ahead and re-tile now, is there any way to preserve some of that work should we eventually take out the built-in tub and put in a freestanding tub? Obviously we'd need to completely redo the tile around the plumbing since that would change, but would it be feasible to simply take out the bottom tiles on the rest and continue down to meet the floor? Or would ripping out the tub do enough damage to the walls and such that salvaging the tilework would be close to impossible?

Hope that question makes sense....just trying to figure out if we can justify spending money on the interim work now if it won't be completely wasted should we actually move forward with the remodel! Thanks for any thoughts.